1. Field of the Invention
The present invention relates to a fixing apparatus that is suitably used for an image forming apparatus employing an electrophotographic method or an electrostatic recording method and fixes an unfixed image. More particularly, the present invention relates to a fixing apparatus including a releasing liquid applying mechanism.
2. Related Background Art
As a fixing apparatus for applying a releasing agent (hereinafter referred to as the xe2x80x9coilxe2x80x9d), such as silicone oil, to a fixing roller, there have conventionally been proposed an apparatus that applies the oil to the fixing roller using felt, an apparatus that draws up the oil using felt and applying the drawn-up oil to the fixing roller through an applying roller, an apparatus that draws up the silicone oil using a draw-up roller, and the like. FIG. 6 attached hereto shows the fixing apparatus that draws up the silicone oil using the draw-up roller.
In the apparatus shown in FIG. 6, symbol P represents an oil pan P as a releasing agent containing means for silicone oil O. A first draw-up roller 43 as a releasing agent drawing-up means is partially immersed in the oil O in the oil pan P, and a second draw-up roller 42 as a releasing agent drawing-up means rotates while contacting the first draw-up roller 43 or with a gap therebetween. The first and second draw-up rollers 42 and 43 are rotatively driven by a driving source (not shown). Further, an applying roller 41 as a releasing agent applying means, which is rotatively driven by a driving source (not shown), rotates in contact with the second draw-up roller 42. The applying roller 41 is freely switched between a position in which the applying roller 41 contacts a fixing roller 4a and a position in which the applying roller 41 is separated from the fixing roller 4a. Alternatively, the applying roller 41 is provided so as to contact the fixing roller 4a at all times. With this construction, the drawn-up oil O is applied to the surface of the fixing roller 4a. 
It should be noted here that reference numeral 4b denotes a pressurizing roller that rotates in pressure contact with the fixing roller 4a. A nip portion between these rollers 4a and 4b heated by halogen heaters 45a and 45b fixes an image by transporting a recording material with pressure thereon. Here, the halogen heaters 45a and 45b are respectively disposed at the centers of the rollers 4a and 4b. Also, a metering blade 44 as a releasing agent regulating means contacts the applying roller 41. The metering blade 44 is biased by a spring 49 so that the metering blade 44 is pressed against the applying roller 41 with constant pressure at all times. Also, the metering blade 44 is made of an elastic body, such as fluororubber. With this construction, the amount of oil on the applying roller 41 is regulated to a predetermined value.
However, the temperature of the releasing agent is lower than that of the fixing roller, so that when the releasing agent is applied onto the fixing roller, the applied releasing agent deprives heat from the surface of the fixing roller.
As a result, the fixability is lowered. In particular, immediately after an apparatus is activated, the temperature of the releasing agent is close to room temperature, which leads to the lowest fixability and may cause fixing failures.
Also, the surface of the fixing roller is formed by coating the surface of a metal core with silicone rubber or fluororubber. With this construction, a certain nip is maintained when a recording material is pinched between the rollers.
Alternatively, there is used a fixing roller that is provided with a Teflon coat due to releasing property. This means that the fixing roller basically has a low heat conduction.
If heat is deprived from the upper surface of such a fixing roller, it takes long time to conduct heat from a lower layer. Consequently, when fixing is successively performed for recording materials, even if there occurs no fixing failure, outputted recording materials vary in glossiness or there appears unevenness on the recording materials. This degrades quality on the recording materials.
An object of the present invention is to provide a fixing apparatus that is capable of suppressing reduction of a temperature of the surface of a fixing rotary body due to a releasing liquid.
Another object of the present invention is to provide a fixing apparatus that prevents variations of glossiness during a successive fixing operation.
Still another object of the present invention is to provide a fixing apparatus comprising a fixing rotary body for fixing an unfixed image on a supporting material, an applying member for applying a releasing liquid onto said fixing rotary body, a containing means for containing the releasing liquid and a supplying member contacting the releasing liquid in the containing means for supplying the releasing liquid to said applying member, wherein the containing means includes an outer vessel and an inner vessel for isolating said supplying member from said outer vessel.
Other objects of the present invention will become apparent from the following description.